Cytokine Storm Syndrome


  • Recently, there has been emerging evidence that a subset of the infected patients develop severe COVID-19 because of an overreaction of their immune systems, which triggers what is known as a “Cytokine Storm Syndrome” (CSS).
  • Till now, various studies have shown that the disease has more severe consequences for those above the age of 60 years, especially those with existing complications such as heart disease, chronic respiratory disease and cancer.
  • But some countries have also reported deaths of younger people, including teenagers, after catching the infection.

First let’s know, what are Cytokines?

  • Cytokines are cell signalling molecules that aid cell to cell communication in immune responses and stimulate the movement of cells towards sites of inflammation, infection and trauma.
  • Examples of cytokines include the agents interleukin and the interferon which are involved in regulating the immune system's response to inflammation and infection.
  • There are more specific names given to cytokines based on either the type of cell that makes them or the action they have in the body:
    • Lymphokines (made by lymphocytes)
    • Monokines (made by monocytes)
    • Chemokines (associated with chemotactic actions)
    • Interleukins (made by one leukocyte but act on other leukocytes)

Functions

  • Acute inflammation
  • Chronic inflammation
  • Regulation of metabolic pathways within cells of muscle, adipose tissue, central nervous system, and liver.

About Cytokines Storm Syndrome (CSS)

  • Cytokine Storm Syndromes (CSS) are a group of disorders representing a variety of inflammatory etiologies with the final common result of overwhelming systemic inflammation, hemodynamic instability, multiple organ dysfunction, and potentially death.
  • CSS is seen as a likely major cause of mortality in both the 1918-20 Spanish Flu , the H1N1 (swine flu) and H5N1 (bird flu) outbreaks in recent years
  • An elevated serum ferritin test is usually done for screening for CSS.

Explanation

  • The immune system gets activated by things that the body does not recognize as its own. These things are called antigens, and include bacteria, fungi and viruses.
  • An effective immune system response involves inflammation, an important and indispensable part of the process.
  • For example, one hurt his knee or ankle — the area of this external injury becomes red and swollen, and the immune system in response deploys white blood cells to the injured area to begin work on repairs.
    Without such an immune response, injuries would not heal, and infections would become deadly.
  • The release of inflammatory mediators increases the blood flow to the area, which allows larger numbers of immune system cells to be carried to the injured tissue, thereby aiding the repairing process.
  • However, if this inflammatory response is not regulated, very dangerous consequences can follow. This is when a ‘cytokine storm’ can be triggered.
  • The damage to the surrounding cells can be catastrophic, leading to sepsis and potentially, death.

Role of Cytokines in Immune System

  • Cytokines are signalling proteins that are released by cells at local high concentrations — a CSS is characterised by the overproduction of immune cells and the cytokines themselves because of a dysregulation in the process.
  • A severe immune reaction, leading to the secretion of too many cytokines in the bloodstream, can be harmful since an excess of immune cells can attack healthy tissue as well.
  • According to the United States National Cancer Institute (NCI), a cytokine storm can occur due to an infection, auto-immune condition, or other diseases.
  • Signs and symptoms include high fever, inflammation (redness and swelling), severe fatigue, and nausea.

CSS Impact in COVID-19 Patient

  • Cytokine storms are not exclusive to coronavirus patients.
  • In the case of any flu infection, a cytokine storm is associated with a surge of activated immune cells into the lungs, which, instead of fighting off the antigen, leads to lung inflammation and fluid build-up, and respiratory distress.
  • Increased pro-inflammatory cytokine responses against human coronaviruses such as SARS-CoV-1 (which caused SARS), SARS-CoV-2 (which is responsible for the current COVID-19 pandemic), and MERS can result in acute lung injury and acute respiratory distress syndrome (ARDS).
  • If the clinical features of CSS are not recognised and adequate treatment is not promptly instituted, it may result in multiple organ failure.

Source : Civil Services Chronicle Online, April, 2020